Further Problems in X-Ray Protection

Abstract

In view of the necessity for protection against stray radiation in photofluorographic units (1, 2), the Tuberculosis Control Division of the U. S. Public Health Service has developed a program of personnel protection which is herein described. In addition to the provision of adequate protective equipment, measures had to be taken to see that such equipment was properly used and that needless exposure was avoided. In doing this it was necessary to take into account the human factor of heedlessness and to see that operators had to take precautions whether or not they wished to do so. These steps having been taken, it was considered essential to determine by physical means whether the protection provided was adequate. Further, in view of the shortcomings of the accepted permissible dose, it was considered advisable to check workers for evidence of injury. It is believed that this program will provide not only the best possible protection but will yield much needed information concerning the problems of exposure and injury. Procedures Location of Equipment: Since the photofluorographic equipment in use is of portable type, operators are directed first of all to give attention to its location and arrangement. Airy, spacious rooms, 18 × 20 feet or larger, are desirable. The equipment should be so arranged that the x-ray beam is directed toward an outside wall, preferably toward a window. The x-ray machine should be at least 8 to 10 feet from side walls in order to reduce reflected radiation and provide adequate freedom of movement of patients and operators. Alignment: Operators are instructed to check alignment with 14 × 17-inch films as described in the first paper of this series (p. 565). In order to keep stray radiation at a minimum, the primary x-ray beam should be limited strictly to the field of the fluoroscopic screen. Such beams can be obtained by properly adjusting the position and angle of the extension cone. Unnecessary Primary Radiation: Some primary radiation escapes through the x-ray tube housing but, as shown in the first paper, this is not the most serious source of stray radiation. Occasionally “leaks” occur in the tube housing due to faulty construction, failure to keep all parts in place, etc. Operators are asked to check for leaks with films and to explore the field around the tube in order to know where the intensity is greatest. Holes in the tube housing should be covered with lead (or other adequate absorbing materials) and the beam of primary radiation confined strictly to the area of the fluorographic screen. The fact that a so-called “ray-proof” tube is being used should not lead to a false sense of security, as the lead housing of such tubes is intended to do no more than cut the escaping radiation to a reasonably safe level. Some idea of the quantity and quality of radiation that will escape from ray-proof tubes operated under a variety of conditions has been given recently in a paper by White, Cowie, and de Lorimier (3).